Download Nile Tilapia Oreochromis niloticus

Nile Tilapia Oreochromis niloticus
1
Taxonomy
Species:
Oreochromis niloticus (Linnaeus 1758)
Family:
Cichlidae
Order:
Perciformes
Class:
Actinopterygii
The Nile tilapia Oreochromis niloticus is a deep-bodied fish with cycloid scales. Silver in colour with
olive/grey/black body bars, the Nile tilapia often flushes red during the breeding season (Picker &
Griffiths 2011) Figure 1). It grows to a maximum length of 62 cm, weighing 3.65 kg (at an estimated 9
years of age) (FAO 2012). The average size (total length) of O. niloticus is 20 cm (Bwanika et al.
2004).
Figure 1.
2
Images of the Oreochromis niloticus (Source: FAO 2012)
Natural distribution and habitat
O. niloticus is native to central and North Africa and the Middle East (Boyd 2004) (Figure 2). It is a
tropical freshwater and estuarine species. It prefers shallow, still waters on the edge of lakes and
wide rivers with sufficient vegetation (Picker & Griffiths 2011).
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Figure 2.
Native (green) and introduced (red) ranges of O. niloticus globally (Data source: GISD 2012). Please
note this map does not indicate country wide presence, but merely that the species is categorised as
an alien within that country.
3
Biology
3.1
Diet and mode of feeding
Nile tilapia are known to feed on phytoplankton, periphyton, aquatic plants, invertebrates, benthic
fauna, detritus, bacterial films (FAO 2012) and even other fish and fish eggs. Depending on the food
source, they will feed either via suspension filtering or surface grazing (GISD 2012), trapping
plankton in a plankton rich bolus using mucus excreted from their gills (Fryer & Iles 1972). O.
niloticus have been observed to exhibit trophic plasticity according to the environment and the
other species they coexist with (Bwanika et al. 2007).
3.2
Growth
Nile tilapia can live longer than 10 years (GISD 2012). Food availability and water temperature
appear to be the limiting factors to growth for O. niloticus (Kapetsky & Nath 1997). Optimal growth
is achieved at 28-36°C and declines with decreasing temperature (Teichert-Coddington et al. 1997,
FAO 2012). The ability to vary their diet may also result in variation in growth (Bwanika et al. 2007).
In aquaculture ponds, O. niloticus can reach sexual maturity at the age of 5-6 months (FAO 2012).
3.3
Reproduction
Male fish initiate breeding with the creation of a spawning nest, which is fiercely guarded. When the
water temperature increases above 24°C, a female will lay her eggs into the nest. These are then
fertilized by the males before the female collects them in her mouth (known as mouth brooding).
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The eggs and the fry which then hatch are incubated and brooded in this manner until the yolk sac is
fully absorbed two weeks later (FAO 2012).
The number of eggs a female will produce is dependent on body size. This can range from 100 eggs
(produced by a 100 g fish) to 1500 eggs (spawned by a 1 kg fish). The females will not spawn while
brooding. Males on the other hand fertilise the eggs of multiple females continuously given optimal
environmental conditions (FAO 2012).
3.4
Environmental tolerance ranges
The Nile tilapia will reportedly thrive in any aquatic habitat except for torrential river systems and
the major factors limiting its distribution are salinity and temperature (Shipton et al. 2008).
The survival limits for O. niloticus are reported to lie between 11 and 42°C (FAO 2012). The
concentration of dissolved oxygen is not a major limiting factor for Nile tilapia, as they can tolerate
levels as low as 3-4 mg/l (Boyd 2004).
4
History of domestication
Nile tilapia have been farmed for centuries. Depictions on an Egyptian tomb (dated at 4000 years)
display the fish in ornamental ponds. The culture of the tilapia genus on a global scale, primarily
Oreochromis mossambicus, began in the 1940s. However, it was not until the 1960s that O. niloticus
was exported worldwide (FAO 2012).
Aquaculture was heralded as the perfect protein production technique for developing countries
during the 1960s and 1970s. Aid organisations promoted aquaculture as a means of improving food
security with low grain to feed conversion rates, and minimal environmental impacts (Canonico et al.
2005).
This global popularity has led to a number of important developments in culture techniques. Initially,
tilapia were allowed to breed freely. However, farmers and scientists observed that this led to the
production of smaller fish. In the 1960s, attempts were made to produce male monosex populations
through hybridisation between different tilapia species (Hickling 1963). This proved problematic and
gradually females reappeared in the progeny (Wohlfarth 1994). Major technological developments
in the 1970s allowed for the successful production of all-male populations through the use of sexreversing hormones which resulted in higher returns from tilapia farming. Following this, and further
research into culture processes, the industry boomed (FAO 2012).
Today, tilapia are often farmed with multiple species in the same pond, such as shrimp and milkfish.
This not only optimises the financial return if space is limited, but also helps prevent the growth of
harmful bacteria and serves to remove excess organic matter in the water (Troell 2009). Genetic
modification of the species has also been undertaken to maximise farming efficiency. For example,
the Genetic Improvement in Farmed Tilapia (GIFT) project in the Philippines created strains of O.
niloticus that grew up to 60% faster than their relatives (Eknath & Acosta 1998). However, in Africa,
the use of improved stock lines is rare due to concerns regarding genetic modification. As a result,
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many tilapia farms use broodstock which underperforms by 20-40% relative to wild individuals.
There is great scope for improvement in this regard, either by rotational mating or the introduction
of improved strains (Brummet & Ponzoni 2009).
5
Introduction and spread (South Africa)
O. niloticus was first introduced to South Africa in 1959 with its release into dams in the Western
Cape and KwaZulu-Natal, as food for bass (van Schoor 1966). However, these initial efforts were
unsuccessful. Since the 1980s, introductions in other parts of Southern Africa has led to fish escaping
into rivers (a phenomenon that has been compounded by intentional introductions by anglers) and
as a result, the Nile tilapia has established self-sustaining wild populations in the Incomati and
Limpopo Rivers (Picker & Griffiths 2011) (Figure 3).
Figure 3.
6
Map of introduced range (red) of O. niloticus within South Africa (Source: M. Picker & C. Griffiths).
Note: not all introductions were successful. In addition, the Incomati River reportedly contains
introduced O. niloticus, although this is not shown here.
Introduction and spread (International)
Globalisation has contributed to the spread of many recreational angling species, with introduced
species being marketed worldwide, and modern transport allowing the relocation of these species
across physical barriers (Cambray 2003).
O. niloticus is one of the top ten introduced species of the world (Picker & Griffiths 2011). To date,
tilapia species have been introduced into more than 90 countries across the world (Figure 2), with
culture farms on every continent except Antarctica (Fitzsimmons 2001).
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7
Compatibility with local environmental conditions
Compatibility of this species to local environmental conditions was evaluated by comparing the
ambient annual temperature ranges of the 31 terrestrial ecoregions of South Africa (Kleynhans et al.
2005) (Figure 4, Table 1) to the known environmental tolerance ranges for O. niloticus (FAO 2012).
From this, it is clear that culture of O. niloticus is possible in at least 12 of the ecoregions in this
country (although some may only be feasible on a seasonal basis):












1. Limpopo Plain;
2. Soutpansberg;
3. Lowveld;
4. North Eastern Highlands;
5. Northern Plateau;
12. Lebombo Uplands;
13. Natal Coastal Plain;
17. North Eastern Coastal Belt;
25. Western Coastal Belt;
28. Orange River Gorge;
30. Ghaap Plateau, and;
31. Eastern Coastal Belt.
Equally, it should be noted that this species is potentially able to establish naturalised populations in
all twelve of these regions. Indeed, O. niloticus has reportedly already been introduced and/or is
currently established in at least four of these twelve regions (Picker & Griffiths 2011). In addition, it
is also established in at least four regions which are ostensibly climatically unsuitable (although
these may be seasonal populations). Established populations have been recorded in the following
regions (Picker & Griffiths 2011):








1. Limpopo Plain;
2. Soutpansberg;
6. Waterberg;
7. Western Bankenveld
8. Bushveld Basin
13. Natal Coastal Plain
16. South Eastern Uplands
17. North Eastern Coastal Belt
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Figure 4.
Map of South African Ecoregions (Kleynhans et al. 2005).
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Table 1.
Altitude and ambient temperature (annual average range and maximum and minimum temperatures
reported) in the 31 ecoregions of South Africa. This information was collated from Kleynhans et al.
2005 and assessed to determine compatibility with O. niloticus culture.
Ecoregion
1. Limpopo Plain
2. Soutpansberg
3. Lowveld
4. North Eastern Highlands
5. Northern Plateau
6. Waterberg
7. Western Bankenveld
8. Bushveld Basin
9. Eastern Bankenveld
10. Northern Escarpment
Mountains
11. Highveld
12. Lebombo Uplands
13. Natal Coastal Plain
14. North Eastern Uplands
15. Eastern Escarpment
Mountains
16. South Eastern Uplands
17. North Eastern Coastal
Belt
18. Drought Corridor
19. Southern Folded
Mountains
20. South Eastern Coastal
Belt
21. Great Karoo
22. Southern Coastal Belt
23. Western Folded
Mountains
24. South Western Coastal
Belt
25. Western Coastal Belt
26. Nama Karoo
27. Namaqua Highlands
28. Orange River Gorge
29. Southern Kalahari
30. Ghaap Plateau
31. Eastern Coastal Belt
Temperature
range (°C)
Mean annual
temp (°C)
O. niloticus
climatic suitability
2 to 32
18 to >22
Y
4 to 32
4 to 32
16 to >22
16 to >22
Y
Y
2 to 32
16 to 22
Y
2 to 30
16 to 20
Y
2 to 32
14 to 22
N
0 to 32
14 to 22
N
0 to 32
14 to 22
N
0 to 30
10 to 22
N
0 to 30
10 to 22
N
-2 to 32
12 to 20
N
6 to 32
8 to 32
0 to 30
18 to >22
20 to >22
14 to >22
Y
Y
N
<-2 to 28
<8 to 18
N
0 to 30
10 to 22
N
4 to 30
16 to 22
Y
-2 to 30
10 to 20
N
0 to 32
10 to 20
N
2 to 30
12 to 20
N
0 to >32
10 to 20
N
4 to 30
10 to 20
N
0 to >32
10 to 20
N
0-300; 300-900 limited
4 to 32
10 to 20
N
0-700, 700-1100 (limited)
300-1700, 1700-1900
(limited)
100-1300; 1300-1500
(limited)
0-1100
500-1700; 1700-1900
(limited)
900-1700
0-500, 500-900 (limited)
2 to >32
16 to 20
Y
0 to >32
12 to 20
N
2 to 32
12 to 20
N
2 to >32
16 to 22
Y
-2 to >32
14 to 22
N
0 to 32
4 to 28
16 to 20
16 to 20
Y
Y
Altitude (m a.m.s.l)
300-1100 (1100-1300
limited)
300-1700
0-700; 700-1300 limited
300-1300 (1300-1500
limited)
900-1500 (1500-1700
limited)
700 –900
9limited), 900-1700
900-1700
700-1700 (1700-1900 very
limited)
500-2300
500-900 (limited) 900-2300
1100-2100, 2100-2300
(very limited)
0-500
0-300
0-100 (limited), 100-1500
1100-3100; 3100-3500
limited
300-500 (limited), 5001700, 1700-2300 (limited)
0-700
100-300 (limited), 3001900, 1900-2100 (limited)
0-300 limited; 300-1900,
1900-2100 (limited)
0-500; 500-1300 limited
100-300 (limited), 3001700; 1700-1900 limited
0-700; 700-1500 (limited)
100-300 (limited), 3001700, 1700-2500 (limited)
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7.1
Culture techniques
Depending on the nature of O. niloticus farming (i.e. seasonal or year-round production) there are
several alternative options for culture. These could be i) seasonal pond culture; ii) seasonal cage
culture in lakes, rivers and dams; or iii) thermally regulated intensive bio-secure recirculation
systems in tanks and raceways (Shipton et al. 2008).
Of these, freshwater cage culture is considered to represent the highest biosecurity risk (i.e. risk of
escapement and/or transfer of pathogens and diseases to wild populations), while culture in
raceways or ponds represent a moderate biosecurity risk, and culture in recirculating systems, a low
biosecurity risk. Biosecurity risks can be further mitigated through a range of control measures listed
in Section 11.
8
Research requirements
The impacts of O. niloticus on native aquatic biodiversity have been well studied in a select few
places around the world (see Section 10.2 below). However, this knowledge base needs to be
expanded so that it is more globally representative. Currently geographic data on O. niloticus in
South Africa refers only to the distribution of the species and there is no information on abundance
at these locations. These data are crucial in determining the true current and future impacts.
GIFT tilapia are widely used in Mozambique and the strain has been recorded in KwaZulu-Natal (KZN)
as well. A research project should be initiated to investigate the impacts of this, particularly the
threat of hybridisation with O. mossambicus.
In addition, research into the impacts of habitat degradation and climate change on O. niloticus
survival are necessary to determine future cumulative impacts.
9
Benefit assessment
The international production of O. niloticus in aquaculture has increased exponentially since the
1950s and now totals 2 538 052 tonnes annually (Figure 5). The value of the fish has followed this
increase and is currently valued at USD4.019 billion (Figure 6).
In 2008, there was only one tilapia farm in South Africa, functioning as a pilot project (Britz et al.
2009). The total South African production of tilapia in 2009 and 2010 was estimated at 10 tonnes
(DAFF 2012a). Tilapia farming in South Africa was valued at ZAR0.3 million in 2008 (Britz et al. 2009).
The South African tilapia pilot farm employed two full time (and no part time) staff in 2008. These
figures are conservative as they include only those involved in primary production and not those
who work in the secondary services (such as feed manufacturers or those employed in fish
processing plants) (Britz et al. 2009).
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Production (tonnes)
3000000
2500000
2000000
1500000
1000000
500000
1950
1953
1956
1959
1962
1965
1968
1971
1974
1977
1980
1983
1986
1989
1992
1995
1998
2001
2004
2007
2010
0
Figure 5.
International production of O. niloticus from 1950-2010 (Source: FAO - Fisheries and Aquaculture Information
and Statistics Service - 10/09/2012)
4500000
Value (USD thousand)
4000000
3500000
3000000
2500000
2000000
1500000
1000000
500000
1950
1953
1956
1959
1962
1965
1968
1971
1974
1977
1980
1983
1986
1989
1992
1995
1998
2001
2004
2007
2010
0
Figure 6.
International value (in USD thousand) of O. niloticus from 1950-2010 (Source: FAO - Fisheries and
Aquaculture Information and Statistics Service - 10/09/2012)
10
Risk assessment
10.1
Likelihood of this species becoming established in South Africa
Nile tilapia have already become established in two river systems in South Africa. Attempts have,
however, been made to intentionally introduce this species to a number of other river systems in the
country (notably in the Western Cape and KwaZulu-Natal), but these have not been successful. It is
not clear therefore, if O. niloticus were introduced to other river systems in the country, whether it
would be able to establish populations in these areas. However, given the fact that the optimal
temperature for growth of this species is listed as ranging from 28-36°C (Teichert-Coddington et al.
1997, FAO 2012), and the fact that females only tend to spawn at temperatures above 24°C, it is
likely that this species would only be able to become established in the tropical, north-eastern sector
of the country. This is consistent with the current distribution range in the Incomati and Limpopo
Rivers (Picker & Griffiths 2011).
The invasive potential of O. niloticus in the nineteen remaining ecoregions of South Africa has been
assessed in accordance with the European Non-Native Species Risk Analysis Scheme (ENSARS) (Copp
et al. 2008) developed by CEFAS (UK Centre for Environment, Fisheries & Aquaculture Science).
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ENSARS provides a structured framework (Crown Copyright 2007-2008) for evaluating the risks of
escape, introduction to and establishment in open waters, of any non-native aquatic organism being
used (or associated with those used) in aquaculture. For each species, 49 questions are answered,
providing a confidence level and justification (with source listed) for each answer. The questions and
results of the assessment on O. niloticus can be found in Appendix 1.
The outcome of the scoring was that O. niloticus should be further evaluated before introduction in
the nineteen remaining ecoregions. Tailored recommendations have thus been developed for the
various different culture techniques available (section 12).
10.2
Potential ecological impacts
Escapees from aquaculture facilities are inevitable and occur worldwide, unless appropriate
mitigatory methods are applied. Due to their ability to adapt to new environments (with rapid
reproduction and spread), O. niloticus have the potential to seriously threaten native biodiversity.
A study by Zengeyah et al. (2011) investigated the stomach contents of tilapiine species in the
Limpopo River Basin to determine the impacts of the alien O. niloticus on the native O. mossambicus
and Tilapia rendalli. O. niloticus and O. mossambicus have high diet overlap whereas T. rendalli
exhibits low diet overlap with O. niloticus. This could result ultimately in the displacement of O.
mossambicus from the Limpopo River, as O. niloticus is known as an aggressive competitor.
Intensively farmed fish can lead to the excretion of high concentrations of nutrients in the water, a
process known as eutrophication. Increased nitrate and phosphate levels (from faeces or uneaten
food) can cause algal blooms (including some toxic species) and mass fish mortality events. In Lago
Paranoa, Brazil, high numbers of O. niloticus have been linked to increases in total phosphorous,
chlorophyll a concentrations and cyanobacteria densities (Starling et al. 2002).
Another source of pollution which may be present in effluent from O. niloticus farms is artificial
hormones. Tilapia farms use 17-methyl testosterone to create all male populations, which have
larger body sizes and are thus more profitable (McIntosh 1982).
Hybrids of O. niloticus and the native O. mossambicus were discovered in dry pools beside the
Limpopo River, alongside pure strains of each species (Moralee et al. 2000). Following mtDNA
genotyping, several O. mossambicus specimens (previously morphologically identified) were
discovered to be hybrids (D’Amato et al. 2007). As a result of hybridisation, O. mossambicus could
lose genetic material (and thus adaptive value) which distinguishes it from O. niloticus. This includes
its drought resistance, tolerance of low temperatures and the ability to survive in high salinity
environments (D’Amato et al. 2007). Hybrids of O. niloticus and O. mossambicus are widely cultured
in South Africa, however it should be recognised that these do not share the same traits as GIFT
strains but they may be morphologically indistinguishable (N. James, Rivendell Hatchery, pers.
comm.).
High stocking densities commonly found in aquaculture farms can lead to outbreaks of parasites and
diseases, if the hatchery design and management is not optimal. Some of the parasites which affect
tilapia may also affect other freshwater finfish. If unknown diseases are introduced, indigenous
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species may not have an adequate immune system to cope with them, and as a result it can lead to
their demise. Risks associated with introduction of diseases and parasites to native species are thus
not insignificant. A summary of symptoms of diseases and/or parasites which have been found
internationally to infect O. niloticus is provided in Table 2. However, to date, none of these diseases
have been found in South African tilapia (DAFF 2012b).
Table 2. Symptoms of the diseases/parasites which commonly infect O. niloticus (Modified from FAO 2012)
Name of disease or parasite
Motile Aeromonas
Septicaemia (MAS)
Vibriosis
Columnaris
Edwardsiellosis
Streptococcosis
Saprolegniosis
Ciliates
Monogenetic trematodes
10.3
Common symptoms
Loss of equilibrium; lethargic swimming; gasping at surface;
haemorrhaged or inflamed fins & skin; bulging eyes; opaque corneas;
swollen abdomen containing cloudy or bloody fluid; chronic with low
daily mortality
Same as MAS
Frayed fins &/or irregular whitish to grey patches on skin &/or fins;
pale, necrotic lesions on gills
Few external symptoms; bloody fluid in body cavity; pale, mottled
liver; swollen, dark red spleen; swollen, soft kidney
Lethargic, erratic swimming; dark skin pigmentation; exophthalmia
with opacity & haemorrhage in eye; abdominal distension; diffused
haemorrhaging in operculum, around mouth, anus & base of fins;
enlarged, nearly black spleen; high mortality.
Lethargic swimming; white, grey or brown colonies that resemble
tufts of cotton; open lesions in muscle
Occurs on gills or skin
Occurs on body surface, fins or gills
Potential socio-economic impacts
Currently there are no commercial freshwater fisheries in South Africa, (B. Clark, Anchor
Environmental, pers. comm.), so this fishery should not suffer significant negative impacts as a result
of further introductions of O. niloticus.
On the other hand, recreational fisheries could be negatively affected by aquaculture production of
O. niloticus if parasites or diseases from farmed populations are allowed to spread to established
wild stocks. The same is presumably applicable to subsistence fisheries as well.
10.4
Risk summary
There is reasonable likelihood that:

There will be escapees from any established culture facility unless best management
practises are followed;
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



11
Unless barriers are provided, O. niloticus could potentially colonise and establish in
previously un-invaded river catchments where it is introduced, but only in the warmer,
tropical parts of the country where this species is able to reproduce successfully;
In these areas, introduced tilapia will compete with and/or predate on indigenous species
and as such may pose a risk to the continued survival of these native fish species especially
those that are already rare or range restricted;
These is a high likelihood that hybridisation will occur with indigenous species (especially
other tilapia species); and
Diseases or parasites could be transferred to populations of indigenous fish species unless
appropriate best management practises are adopted, and all individuals are certified disease
free by suitably qualified veterinarians prior to introduction.
Control and prevention options
There are a number of control options for limiting the introduction and spread of alien freshwater
fish species in South Africa. O. niloticus has already established in at least two river systems in South
Africa. The focus thus needs to be on preventing their spread or deliberate introduction to new
areas or river systems, as well as seeking to eradicate these fish from systems where their impact on
biodiversity is considered to be unacceptably high.
Controlling the spread of invasive species through prevention is thought to be the most costeffective means (Leung et al. 2002). The Department of Environmental Affairs & Development
Planning Generic Environmental Best Management Practice Guideline for Aquaculture Development
and Operation in the Western Cape (Hinrichsen 2007) should be used as a guide for construction of
facilities and management thereof. These measures can serve to reduce biosecurity risks for more
risky culture techniques such as pond culture from moderate to high or from moderate to low. Key
points from these guidelines are summarised below.
It is recommended that all new land-based aquaculture facilities should be built above the 1 in 50
year flood line, with infrastructure built to resist the impacts of floods or tidal currents (Hinrichsen
2007). The creation of physical barriers around the facility can also be effective in preventing spread
of invasive species (Novinger & Rahel 2003). For example, weirs can help to prevent upstream
invasions (although the impacts of this construction to the ecosystem must also be considered prior
to permit authorisation) (Driver et al. 2011). Secure fencing around the aquaculture facility in
combination with restricted access will prevent any person intentionally removing live individuals
(Hinrichsen 2007).
In order to decrease the risk of escapes, pond and dam culture systems should be designed with
stable walls (free from tree roots or burrowing animals) at a suitable gradient. Water levels should
be monitored to determine flood threats and also be built with a capacity for overflow, with an
option to be drained completely. All outlet and inlet pipes should have mesh screens which will
prevent the escape of eggs from the hatchery and fry from the grow-out facilities. These criteria are
also recommended for tank culture systems. The most risky of production systems, cage culture,
must have clearly demarcated cages which are built to handle severe weather conditions, with
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double netting where possible. Anchorage lines and cage netting should be inspected regularly for
tears or biofouling (Hinrichsen 2007).
Tilapia species are known to reproduce prolifically (often before obtaining market size), much to the
chagrin of commercial farmers. One solution to this (which would also limit the impacts of
aquaculture in South Africa) is triploidy, the production of sterile offspring. In addition, many
aquaculture facilities farm triploids (by heating normal female eggs) or using a monosex culture of
males (FAO 2012). These animals are unlikely to reproduce as wild populations, if they were to
escape.
There is only one example globally of an O. niloticus established population being successfully
eradicated. Eradication methods can be mechanical or chemical. Mechanical eradication techniques,
such as electrofishing, netting or controlled angling are time consuming and not considered to be
very cost-effective (Bainbridge et al. 2005). Alternatively, piscicides, such as rotenone, can be used
to control O. niloticus numbers. The nation state of Palau used Rotenone to successfully eradicate
tilapia from five invaded locations on the island (GISD 2012). Alternatively, botanical piscicides can
be used as a control which is effective but less toxic (Caguan et al. 2004).
The creation of tilapia farmers associations in most producing countries has been encouraged and
facilitated (FAO 2012). These associations should encourage their members to adhere to the rules of
the FAO Code of Conduct for Responsible Fisheries and the FAO Technical Guidelines for Responsible
Fisheries (Aquaculture Development). Given that commercial farmers require a licence and must
comply with regulations, they are unlikely to intentionally encourage the spread of O. niloticus.
However, there is an issue with informal trading of live tilapia, especially following the closure of
many government hatcheries. The remaining hatcheries must be regulated and all fingerling should
be certified prior to sale (B. Van der Waal, private consultant, pers. comm.).
12
Recommendations regarding suitability for use in aquaculture in South
Africa
In South Africa, National Freshwater Ecosystem Priority Areas (NFEPA) guidelines provide strategic
spatial priorities for conserving South Africa’s freshwater ecosystems and supporting sustainable use
of water resources. The NFEPA guidelines were designed to assist those involved in the conservation
and management of FEPAs, to preserve these important areas in the high quality condition they
currently exist. FEPAs are river or wetland areas which are in a largely unmodified/natural condition.
These can include free-flowing rivers (free from dam structures), habitats which support threatened
species and their migration corridors, areas which are relied upon as a water source for catchments,
or simply provide a representative selection of wetland types. Rivers and their associated subquaternary catchments which were determined important areas in protecting viable populations of
threatened and near-threatened fish are broadly termed Fish Sanctuaries.
Figure 7 displays the location of FEPAs and their associated sub-quaternary catchments (blue
shading). Fish sanctuaries which are deemed to be of high ecological condition were also assigned
FEPA status and accordingly, for the purpose of this study, we have grouped together Fish and River
FEPAs. Fish sanctuaries that are not in as good condition but nonetheless recognised as vital to the
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protection of threatened fish species, were classified as Fish Support Areas (green shading). Fish
migration corridors represent areas for potential migration between essential habitats (yellow
shading). Upstream Management Areas require protection to prevent degradation of downstream
areas (brown shading). Phase 2 FEPA sub- quaternary catchments (pink shading) include riverine
areas that are in a poorer ecological condition but nonetheless still considered important for
conservation of freshwater aquatic resources provided they can be rehabilitated. Rehabilitation of
these areas is expected to be undertaken when all other FEPAS are considered well managed.
Collectively, these areas all represent important habitats and sites for the conservation of freshwater
biodiversity in South Africa and should be protected from development and other adverse impacts.
FEPA maps are also considered to be directly relevant to the National Environmental Management:
Biodiversity Act (Act No. 10 of 2004; RSA, 2004) (hereafter referred to as NEM:BA), as they inform
both the listing of threatened freshwater ecosystems and the process of bioregional planning
provided for by this Act. FEPA maps support the implementation of the National Environmental
Management: Protected Areas Act (Act No. 57 of 2003; RSA, 2003) (hereafter referred to as the
Protected Areas Act) by informing the expansion of the protected area network (Driver et al. 2011).
In spite of their value in conservation planning and management, FEPAs are considered to be of
lesser value in guiding decision making regarding allocation of aquaculture permits for alien species
such as O. niloticus. This is because FEPAs tend to cover restricted conservation worthy aquatic
ecosystems within river basins or sub quaternary catchments that are by nature linked to the rest of
the catchment by existing river channels. Alien fish, being mostly highly mobile, can very easily
invade an area designated as a FEPA from virtually any other portion of the catchment except where
a barrier (such as a dam wall or waterfall) prevents this from happening. In addition, it does not offer
a species-specific approach i.e. the FEPAs recommend that no species be farmed in these areas.
However, not all species will impact on threatened native species in an equal manner.
For this reason a complimentary mapping process (termed the NEM:BA AIS fish maps, Swartz 2012)
was initiated specifically to support the process of identifying locations for the farming of alien
invasive freshwater fish species. These maps are based on the same sub-quaternary layers as utilised
in the FEPA process, and are thus compatible with the NFEPA maps. Biodiversity protection was
maximised wherever possible in both sets of maps, however, no consideration was given to climatic
suitability for the non-indigenous species of concern. The NEM:BA maps were created using known
distribution records and expert opinion. These maps were then developed in consultation with
anglers and aquaculturists to take into account socio-economic impacts of the zonation process (O.
Weyl, SAIAB, pers. comm.).
A NEM:BA AIS fish map has been prepared for Nile tilapia on the premise that O. niloticus is a
NEM:BA List 3: Category 2 species i.e. one to be managed by area. Category 2 species generally have
high economic value for aquaculture and angling, but have a high potential negative impact on the
environment where they occur outside their native range. In the case of O. niloticus, it is classed as a
species with a risk of genetic contamination.
Page | 14
Figure 7.
South Africa’s Ecoregions with FEPAs, Fish Support areas, Fish Corridors, Upstream Management Areas and Phase 2 FEPAs. Source: Kleynhans et al. 2005 and Nel 2011.
Page | 15
These maps have not been implemented by government as part of the legislative regime as yet,
owing to the fact that NEM:BA currently does not allow for the approach of regulating these species
as envisaged by the maps. As a result, they have not been included in this Biodiversity Risk and
Benefit Assessment profile.
It is recommended that conservation authorities responsible for evaluating aquaculture permit
applications should make use of all of the available resources including the FEPA maps and
ecoregions maps as well as the NEM:BA AIS fish maps when these are released, to inform their
decision making processes. However, this remains a complex procedure, despite the availability of
these visual tools, therefore further consultation with experts may be necessary.
At present, in the absence of the NEM:BA AIS maps, recommendations for O. niloticus culture
activities have been based on the FEPA maps (Figure 7) and physiological tolerance limits for the
species (Table 1). In the first instance, it is recommended that no permits for culture activities be
issued in areas designated as FEPAs (Table 3).
Table 3.
Recommendations for O. niloticus culture in South Africa. Red shading indicates ‘No culture”, orange shading
indicates “high biosecurity” (closed RAS only), blue shading indicates “medium biosecurity” (i.e. partial RAS)
and green shading indicates “low biosecurity” requirements (i.e. dam, river or cage culture). White blocks
represent “Non-applicability”, i.e. in this case, there is no native distribution of O. niloticus in South Africa.
Some of the ‘high biosecurity’ categories require further explanation and this is denoted with a number. ‘1’
has been categorised as high biosecurity to include the protection of non-fish threatened species (which are
not directly recognised in the fish sanctuary format of FEPAs).
FEPA map category
Native
distribution
Existing
introduced
population
FEPA (Fish and River FEPAs)
Species not
present
(climatically
suitable)
1
Species not
present
(climatically
unsuitable)
1
1
Fish Support Area
Fish Corridor
Upstream management Area
Phase 2 FEPAs
1
1
1
All other areas
In all areas (with the exception of FEPAs), where the species is currently not present, but the climate
is suitable, culture can be undertaken only following implementation of high biosecurity facilities
(i.e. closed Recirculating Aquaculture Systems, RAS). Also, in all Phase 2 FEPAs, aquaculture facilities
must have high biosecurity measures in place, in order to protect non-fish species which are
threatened and may not be directly protected in the FEPAs or Fish Support Areas. Fish Support Areas
which do not contain O. niloticus, and the climate is deemed unsuitable, should be approached using
the same strict guidelines.
Where there is an existing population of O. niloticus (or O. niloticus hybrids) in Fish Support Areas,
Fish Corridors or Upstream Management Areas, culture activities should be restricted to those with
medium biosecurity measures in place (for example, partial RAS). In all other non-demarcated
Page | 16
freshwater areas, low biosecurity culture facilities can be installed, such as dam, river or cage
culture.
In Fish Corridors, Upstream Management Areas and all remaining freshwater area, where the
species is not found (and is the climate is not suitable for the species to survive in the natural
environment), dam, river or cage culture can be undertaken (low biosecurity). This should be
undertaken in conjunction with single sex populations and/or triploid individuals.
It is recommended that cage culture of O. niloticus should be avoided in ecoregions which contain
native populations of O. mossambicus, due to the risk of hybridisation, specifically:








3. Lowveld
4. North Eastern Highlands;
12. Lebombo Uplands;
13. Natal Coastal Plain;
14.North Eastern Uplands
16. South Eastern Uplands
17. North Eastern Coastal Belt;
31. Eastern Coastal Belt.
The construction of closed and partial recirculating facilities which treat water and use recycled
water should be encouraged wherever possible, to prevent the discharge of organisms and waste
products into the surrounding environment.
Given the adherence to responsible aquaculture practises, the risks associated with introducing O.
niloticus are reduced. Shipton et al. (2008) discussed the potential for three culture options for O.
niloticus in the Eastern Cape. The authors ruled out semi-intensive seasonal pond culture and semiintensive seasonal cage culture in lakes, rivers and dams deeming thermally-regulated intensive biosecure recirculation systems in tanks and raceways to be the most suitable and least risky.
In the European Union, establishments that are considered “closed” (i.e. 100% biosecure) are
exempt from biodiversity regulations. Owing to the fact that optimum growth is only reached at the
warmer temperatures it is also more feasible in many areas of South Africa to culture them in
temperature regulated closed systems. However, there are considerable cost implications involved
with such intensive designs.
13
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gene flow in an endangered native tilapia fish (Oreochromis esculentus) compared to
invasive Nile tilapia (Oreochromis niloticus) in Yala swamp, East Africa. Conservation
Genetics 12: 243–255.
Bainbridge, W., Alletson, D., Davies, M., Lax, I. & Mills, J. 2005. The Policy of FOSAF on the Presence
of Trout in the Freshwater Aquatic Systems of South and Southern Africa : Position Paper
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No. 3. Environmental Commitee, Federation of Southern African Flyfishers. Unpublished
report, FOSAF Secretariat, Johannesburg. 17 pp.
Boyd, E.C. 2004. Farm-Level Issues in Aquaculture Certification: Tilapia. Report commissioned by
WWF-US in 2004. Auburn University, Alabama 36831.
Britz, P.J., Lee, B. & Botes, L. 2009. AISA 2009 Aquaculture Benchmarking Survey: Primary Production
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Brummett, R.E. & Ponzoni, R.W. 2009. Concepts, Alternatives, and Environmental Considerations in
the Development and Use of Improved Strains of Tilapia in African Aquaculture. Reviews in
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Bwanika, G.N., Makanga, B., Kizito, Y., Chapman, L.J. & Balirwa, J. 2004. Observations on the biology
of Nile tilapia, Oreochromis niloticus, L., in two Ugandan Crater lakes. African Journal of
Ecology 42: 93–101.
Bwanika, G., Murie, D. & Chapman, L. 2007. Comparative Age and Growth of Nile tilapia
(Oreochromis niloticus L.) in Lakes Nabugabo and Wamala, Uganda. Hydrobiologia 589: 287301.
Caguan, A.G., Galaites, M.C. and Fajardo, L.J. 2004. Evaluation of botanical piscicides on Nile tilapia
Oreochromis niloticus L. and mosquito fish Gambusia affinis Baird and Girard. Proceedings
on ISTA, 12-16 September. Manila, Phillipines: 179-187.
Cambray, J.A. 2003. Impact on indigenous species biodiversity caused by the globalization of alien
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Canonico, G., Arthington, A., McCrary, J.K. & Thieme, M.L. 2005. The effects of introduced tilapias
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G., MacLeod, A., Midtlyng, P.J., Miossec, L., Nunn, A.D., Occhipinti-Ambrogi, A., Oidtmann,
B., Olenin, S., Peeler, E., Russell, I.C., Savini, D., Tricarico, E. & Thrush, M. 2008. Risk
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Driver, A., Nel, J.L., Snaddon, K., Murray, K., Roux, D., Hill, L., Swartz, E.R., Manuel, J. & Funke, N.
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Research 25: 781–788.
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the exotic Nile tilapia, Oreochromis niloticus and indigenous tilapiine cichlids in a subtropical
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Page | 20
Appendix 1. Risk scoring methodology for O. niloticus and guidance supplied by the F-ISK toolkit (Copp et al. 2008)
Question
1
2
3
4
5
6
7
8
9
10
11
12
Risk query:
Biogeography/historical
Reply
Is the species highly domesticated or cultivated for commercial, angling or ornamental purposes? Guidance: This taxon
must have been grown deliberately and subjected to substantial human selection for at least 20 generations, or is known
to be easily reared in captivity (e.g. fish farms, aquaria or garden ponds).
Has the species become naturalised where introduced? Guidance: The taxon must be known to have successfully
established self-sustaining populations in at least one habitat other than its usual habitat (eg. Lotic vs lentic) and persisted
for at least 50 years (response modifies the effect of Q1).
Does the species have invasive races/varieties/sub-species? Guidance: This question emphasizes the invasiveness of
domesticated, in particular ornamental, species (modifies the effect of Q1).
Is species reproductive tolerance suited to climates in the risk assessment area (1-low, 2-intermediate, 3-high)? )?
Guidance: Climate matching is based on an approved system such as GARP or Climatch. If not available, then assign the
maximum score (2).
What is the quality of the climate match data (1-low; 2-intermediate; 3-high)? )? Guidance: The quality is an estimate of
how complete are the data used to generate the climate analysis. If not available, then the minimum score (0) should be
assigned.
Does the species have broad climate suitability (environmental versatility)? Guidance: Output from climate matching
can help answer this, combined with the known versatility of the taxon as regards climate region distribution. Otherwise
the response should be based on natural occurrence in 3 or more distinct climate categories, as defined by Koppen or
Walter (or based on knowledge of existing presence in areas of similar climate).
Is the species native to, or naturalised in, regions with equable climates to the risk assessment area? Guidance: Output
from climate matching help answer this, but in absence of this, the known climate distribution (e.g. a tropical, semitropical, south temperate, north temperate) of the taxons native range and the ‘risk are’ (,e, country/region/area for
which the FISK is being run) can be used as a surrogate means of estimating.
Does the species have a history of introductions outside its natural range? Guidance: Should be relatively well
documented, with evidence of translocation and introduction.
Has the species naturalised (established viable populations) beyond its native range? Guidance: If the native range is
not well defined (i.e. uncertainty about it exists), or the current distribution of the organism is poorly documented, then
the answer is “Don’t know”.
In the species' naturalised range, are there impacts to wild stocks of angling or commercial species? Guidance: Where
possible, this should be assessed using documented evidence of real impacts (i.e. decline of native species, disease
introduction or transmission), not just circumstantial or opinion-based judgments.
In the species' naturalised range, are there impacts to aquacultural, aquarium or ornamental species? Guidance:
Aquaculture incurs a cost from control of the species or productivity losses. This carries more weight than Q10. If the
types of species is uncertain, then the yes response should be placed here for more major species, particularly if the
distribution is widespread.
In the species' naturalised range, are there impacts to rivers, lakes or amenity values? Guidance: documented evidence
that the species has altered the structure or function of natural ecosystems.
Page | 21
Comments & References
Certainty
Y
FAO 2012
4
Y
Picker & Griffiths 2011
4
Y
GISD 2012
4
1
Could be seasonally
3
2
Kleynhans et al. 2005
3
N
FAO 2012; Boyd 2004
3
N
Picker & Griffiths 2011
3
Y
Fitzsimmons 2001
4
Y
Picker & Griffiths 2011
4
Y
Van der Waal 2001
4
?
No record of this
2
Y
Starling et al. 2002
4
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
Does the species have invasive congeners? Guidance: One or more species within the genus are known to be serious
pests.
Is the species poisonous, or poses other risks to human health? Guidance: Applicable if the taxon’s presence is known,
for any reason, to cause discomfort or pain to animals.
Does the species out-compete with native species? Guidance: known to suppress the growth of native species, or
displace from the microhabitat, of native species.
Is the species parasitic of other species? Guidance: Needs at least some documentation of being a parasite of other
species (e.g. scale or fin nipping such as known for topmouth gudgeon, blood-sucking such as some lampreys)
Is the species unpalatable to, or lacking, natural predators? Guidance: this should be considered with respect to where
the taxon is likely to be present and with respect to the likely level of ambient natural or human predation, if any.
Does species prey on a native species (e.g. previously subjected to low (or no) predation)? Guidance: There should be
some evidence that the taxon is likely to establish in a hydrosystem that is normally devoid of predatory fish (e.g.
amphibian ponds) or in river catchments in which predatory fish have never been present.
Does the species host, and/or is it a vector, for recognised pests and pathogens, especially non-native? Guidance: The
main concerns are non-native pathogens and parasites, with the host being the original introduction vector of the disease
or as a host of the disease brought in by another taxon.
Does the species achieve a large ultimate body size (i.e. > 10 cm FL) (more likely to be abandoned)? Guidance: Although
small-bodied fish may be abandoned, large-bodied fish are the major concern, as they soon outgrow their aquarium or
garden pond.
Does the species have a wide salinity tolerance or is euryhaline at some stage of its life cycle? Guidance: Presence in
low salinity water bodies (e.g. Baltic Sea) does not constitute euryhaline, so minimum salinity level should be about 15% o.
Is the species desiccation tolerant at some stage of its life cycle? Guidance: Should be able to withstand being out of
water for extended periods (e.g. minimum of one or more hours).
Is the species tolerant of a range of water velocity conditions (e.g. versatile in habitat use)? Guidance: Species that are
known to persist in a wide variety of habitats, including areas of standing and flowing waters (over a wide range of
Velocities: 0 to 0.7 m per sec).
Does feeding or other behaviours of the species reduce habitat quality for native species? Guidance: There should be
evidence that the foraging results in an increase in suspended solids, reducing water clarity (e.g. as demonstrated for
common carp).
Does the species require minimum population size to maintain a viable population? Guidance: If evidence of a
population crash or extirpation due to low numbers (e.g. overexploitation, pollution, etc.), then response should be ‘yes’.
Is the species a piscivorous or voracious predator (e.g. of native species not adapted to a top predator)? Guidance:
Obligate piscivores are most likely to score here, but some facultative species may become voracious when confronted
with naïve prey.
Is the species omnivorous? Guidance: Evidence exists of foraging on a wide range of prey items, including incidental
piscivory.
Is the species planktivorous? Guidance: Should be an obligate planktivore to score here.
Is the species benthivorous? Guidance: Should be an obligate benthivore to score here.
Page | 22
Y
GISD 2012
4
N
No reference
4
Y
Goudswaard et al. 2002;
Angienda et al. 2011
4
N
No reference
4
N
No reference
4
N
No record of this
3
Y
FAO 2012
4
Y
Bwanika et al. 2004
4
N
No record of this
4
N
No reference
4
Y
Tsadik & Bart 2007
3
Y
Goudswaard et al. 2002;
Angienda et al. 2011
4
Y
Need certain number to
prevent inbreeding (no ref)
3
N
can be omnivorous (Bwanika
et al. 2007)
3
Y
Bwanika et al. 2007
4
Y
Y
FAO 2012; Bwanika et al. 2007
FAO 2012
4
4
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
Does it exhibit parental care and/or is it known to reduce age-at-maturity in response to environment? Guidance:
Needs at least some documentation of expressing parental care.
Does the species produce viable gametes? Guidance: If the taxon is a sub-species, then it must be indisputably sterile.
Does the species hybridize naturally with native species (or uses males of native species to activate eggs)? Guidance:
Documented evidence exists of interspecific hybrids occurring, without assistance under natural conditions.
Is the species hermaphroditic? Guidance: Needs at least some documentation of hermaphroditism.
Is the species dependent on presence of another species (or specific habitat features) to complete its life cycle?
Guidance: Some species may require specialist incubators (e.g. unionid mussels used by bitterling) or specific habitat
features (e.g. fast flowing water, particular species of plant or types of substrata) in order to reproduce successfully.
Is the species highly fecund (>10,000 eggs/kg), iteropatric or have an extended spawning season? Guidance: Normally
observed in medium-to-longer lived species.
What is the species' known minimum generation time (in years)? Guidance: Time from hatching to full maturity (i.e.
active reproduction, not just presence of gonads). Please specify the number of years.
Are life stages likely to be dispersed unintentionally? Guidance: Unintentional dispersal resulting from human activity.
Are life stages likely to be dispersed intentionally by humans (and suitable habitats abundant nearby)? Guidance: the
taxon has properties that make it attractive or desirable (e.g. as an angling amenity, for ornament or unusual
appearance).
Are life stages likely to be dispersed as a contaminant of commodities? Guidance: Taxon is associated with organisms
likely to be sold commercially.
Does natural dispersal occur as a function of egg dispersal? Guidance: there should be documented evidence that eggs
are taken by water currents or displaced by other organisms either intentionally or not.
Does natural dispersal occur as a function of dispersal of larvae (along linear and/or 'stepping stone' habitats)?
Guidance: There should be documented evidence that larvae enter, or are taken by, water currents, or can move
between water bodies via connections
Are juveniles or adults of the species known to migrate (spawning, smolting, feeding)? Guidance: There should be
documented evidence of migratory behavior, even at a small scale (tens or hundreds of meters).
Are eggs of the species known to be dispersed by other animals (externally)? Guidance: For example, are they moved by
birds accidentally when the water fowl move from one water body to another?
Is dispersal of the species density dependent? Guidance: There should be documented evidence of the taxon spreading
out or dispersing when its population density increases.
Any life stages likely to survive out of water transport? Guidance: There should be documented evidence of the taxon
being able to survive for an extended period (e.g. an hour or more) out of water. PLEASE NOTE THAT THIS IS SIMILAR TO
QUESTION 22. THIS IS AN ERROR WITH THE FISK TOOLKIT AND THE CREATORS WILL BE ALERTED. FOR THE PURPOSES OF
THIS STUDY, THE ANSWER HAS BEEN REPEATED.
Does the species tolerate a wide range of water quality conditions, especially oxygen depletion & high temperature?
Guidance: This is to identify taxa that can persist in cases of low oxygen and elevated levels of naturally occurring
chemicals (e.g. ammonia).
Page | 23
Y
Mouth brooding (FAO 2012)
4
Y
No reference
4
Y
Moralee et al. 2000
4
N
No reference
4
N
No reference
4
N
FAO 2012
4
Y
Can breed after 5/6 months
(FAO 2012)
Boyd 2004
N
No record of this
3
N
Depends on management
practices
3
N
FAO 2012
4
N
FAO 2012
4
N
No reference
4
?
No record of this
2
?
No record of this
2
N
No reference
3
Y
FAO 2012, Boyd 2004
4
1
4
4
47
48
49
Is the species susceptible to piscicides? Guidance: There should be documented evidence of susceptibility of the taxon to
chemical control agents.
Does the species tolerate or benefit from environmental disturbance? Guidance: The growth and spread of some taxa
may be enhanced by disruptions or unusual events (floods, spates, desiccation), especially human impacts.
Are there effective natural enemies of the species present in the risk assessment area? Guidance: A known effective
natural enemy of the taxon may or may not be present in the Risk Assessment area. The answer is ‘Don’t know’ unless a
specific enemy/enemies is known.
Page | 24
Y
Caguan et al. 2004
4
Y
Boyd 2004
4
?
No record of this
2